Cooling system including a controlled atmospheric heat rejection cycle with water re-capture

ABSTRACT

The present disclosure relates to a cooling system including a controlled atmospheric heat rejection cycle with water re-capture. The cooling system for cooling a heat load includes a first evaporative section configured to circulate a first fluid to enable heat transfer from the heat load to the first fluid, a second evaporative section in fluid communication with the first evaporative section and configured to circulate the first fluid, and a liquid refrigerant distribution unit in thermal communication with the second evaporative section. The liquid refrigerant distribution unit is configured to circulate a second fluid to enable heat transfer from the first fluid to the second fluid.

BACKGROUND

Evaporative cooling systems are commonly employed to remove waste heatin many applications and are usually referred to as cooling towers,evaporative coolers, or fluid coolers because they are often configuredin a tower structure that facilitates the evaporative cooling process.Unlike a dry cooler process, which strictly relies on dry bulb ambientconditions as a means to reject heat and is therefore limited in how lowa returning coolant fluid temperature can be achieved, the evaporativeprocess utilizes water, in either a spray mist, drizzle, or water falltype process to enable contact time with the wet bulb atmosphere toeffectively reject heat and produce lower coolant fluid temperatures.Such systems are two or three component fluid cooling systems in whichair and water or, in some instances, glycol are the only fluids involvedin the evaporative cooling process.

The process of evaporative heat rejection is far more energy efficientthan alternative dry cooling heat rejection processes. However, the downside of the process of evaporative heat rejection is that a significantamount of water is consumed and evaporated into the atmosphere. Sincewater is a precious resource, and has limited availability in certainregions, the process of evaporative heat rejection has an impact on theearth's water resources.

The process of rejecting heat into the atmosphere currently relies oncooling towers, fluid coolers, and evaporative coolers that are simplecycles, of pumping, evaporating, and discharging heat and vapor. Thisequipment is not easily controlled to effectively limit water use orcapture the latent vapor that is expelled into the atmosphere.

Existing water cooled heat rejection equipment has significant inherentlimitations in its ability to produce coolant fluids beyond a minimumleaving water temperature. This is commonly referred to as the wet bulbapproach temperature.

Also, existing water cooled heat rejection equipment has significantinherent limitations in its ability to change and optimize coolantproduction operation over a full spectrum of environmental weather andload conditions. The performance capabilities of this equipment arelimited to, and reliant on, the present environmental enthalpy valueduring operation.

Further, existing water cooled heat rejection equipment requiresignificant chemical treatment systems in order to control internal andexternal biological hazards, in addition to corrosion issues in the pipesystem.

Still further, existing heat rejection equipment is limited by its airflow patterns. This heat rejection equipment provides either a 100% drawthrough or 100% blow through air exchange of air from the environment tothe environment. This equipment uses full air pass through cycles. Thecoolant production process can be varied by varying the production waterflow rates (basin pumps on or off), the coolant flow rates (condenserwater pumping variable frequency drives (VFDs) or speed controls), orthe air flow rates (fan VFDs or speed controls).

However, the existing heat rejection equipment (e.g., towers, fluidcoolers, or evaporative coolers) are not capable of effectivelycontaining, capturing, or processing the discharge vapor that isexpelled to the atmosphere in the process.

In addition, existing heat rejection equipment (e.g., towers, fluidcoolers, or evaporative coolers) is not capable of producing potable(distilled) water as a by product of the cycle.

Also, existing cooling towers cannot be easily operated as free coolerswhen operated in sub-freezing conditions.

SUMMARY

The present disclosure relates to a controlled atmospheric heatrejection cycle with a water reclamation process that can be used inplace of traditional evaporative coolers or dry coolers. The benefitsare numerous. The cycle has the ability to be operated as a waterconservation unit, or is capable of processing clean water from theatmosphere as well as reclaiming the water that is created from thevapor produced in a heat rejection cycle. The unit is designed tooperate and optimize energy use through a wide spectrum of openatmospheric conditions similar to a standard evaporative process. Italso has the ability to systematically control the introduction ofoutside atmospheric air by regulating its introduction in order toprovide a proportionally balanced atmosphere within the apparatus.

This proportional regulation and control between the atmosphere, the inseries refrigerant and air cycles, and the manner with which the vaporis captured enables the apparatus to operate most efficiently across abroad operational spectrum. The unit can efficiently produce clean waterat greatly reduced energy cost. It can optimize the consumption of waterthat is typically consumed in a traditional evaporative process. It canalso significantly reduce the electrical impact of chillers and otherheat producing equipment by effectively delivering lower temperature andbetter quality transport cooling process water at all times.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic flow diagram illustrating a liquidrefrigerant-assisted evaporative cooling system according to anembodiment of the present disclosure; and

FIG. 2 is a schematic flow diagram illustrating the liquid refrigerantassist system for the evaporative cooling system in which evaporationcoils illustrated in FIG. 1 are positioned at an angle with respect tothe horizontal axis.

DETAILED DESCRIPTION

The present disclosure relates to a system that is capable of operatingas an evaporative cooler, dry cooler, water recovery unit, and chilleroptimization circuit. The system includes a housed enclosure includingmodulating intake and discharge dampers. Modulation of the dampersenables full proportional control of the air intake from and airdischarge to the external environment, as well as regulation of theamount and quality of air that is taken and rejected (enthalpy control).The spray water cycle and collection basin allows the apparatus to actas an evaporative cooler.

The in-series evaporator coils are capable of reducing the high latentair sufficiently below the dew point in order to extract water from thehigh latent vapor. The coils can also be utilized to lower the effectivewet bulb condition ahead of the heat rejection coil, thereby creating a“false atmosphere” that is more beneficial for producing cooler leavingwater off the heat rejection coil or coils. By placing the coils inseries, the cycle is enabled to cool the latent air in steps. The air iscooled as it enters the primary heat exchanger evaporator coil.

The heat absorption is accomplished by rejecting the heat through theprocess of latent heat of vaporization. The heat is absorbed into thepumped liquid refrigerant that is present at the evaporator heatexchanger. The refrigerant cycle utilizes a pump to deliver liquidrefrigerant to the evaporator coil. It is an “over-feed” or over-pumpedsystem. The amount of heat that is absorbed at the primary coil isdependent on the rate of boil off of the refrigerant.

The boil-off temperature set point (condensing line) is set at theprimary condenser. The primary circuit is capable of cooling the highlatent air down (discharge air) to within approximately eight degrees ofthe wet bulb temperature. The leaving air temperature can be furtherreduced by enabling the compressor circuit to lower the enteringcondenser water temperature to the main condenser, or the primarycompressor may stay off, and the balance of the air cooling can beaccomplished with the secondary evaporator cycle.

The secondary evaporator circuit has similar operational characteristicsat the primary circuit. However, the effective load on the secondarycompressor is significantly reduced because much of the heat has alreadybeen rejected at the primary evaporator coil. A pumped water cooledcondenser cycle is in series with the basin collection pan, the airstream (spray nozzles), and the water-cooled condenser that rejects theheat from the evaporator coils that are in the air stream. The air atthe intake and at the discharge can be varied from 100% fresh air to 0%fresh air depending on the load, the environmental conditions, and thedesired operational mode such as: water recovery, free cooling, liquidrefrigerant assist, or a combination of these modes.

More particularly, referring to FIGS. 1 and 2, there is illustratedliquid refrigerant-assisted evaporative cooling system 100 according toan exemplary embodiment of the present disclosure. A cooling tower 102,shown generally by the dashed lines and as described in more detailbelow, may include an air intake hood 104 having air intake dampers 104′on one side of the cooling tower 102 that provides an air intakepathway. The cooling tower 102 may also include an exhaust or reliefhood 106 having exhaust dampers 106′ on another side of the coolingtower 102 that provides an exhaust air pathway. The flow of air throughthe air intake dampers 104′ is indicated by arrow 10. The flow of airfrom the exhaust dampers 106′ is indicated by arrow 20.

A liquid refrigerant assist cycle 200, which is described in more detailbelow with respect to FIG. 2, is included within the cooling tower 102within a lower section 102 a of the cooling tower 102 that functions asa Cooling Distribution Unit (CDU) mechanical section or liquidrefrigerant distribution unit. Those skilled in the art will recognizethat the CDU mechanical section within the lower section 102 a may alsobe configured as a stand-alone CDU mechanical section.

The evaporative cooling system 100 is in thermal communication with ageneralized heat load 50 via a cooling water return (or refrigerant orany other process cooling fluid) header 120 a from the heat load 50 anda cooling water (or refrigerant) supply header 120 b. For the purposesof illustration herein, the return header 120 a and the supply header120 b are described herein as cooling water return header 120 a andcooling water supply header 120 b although a refrigerant or any otherprocess cooling fluid may flow through the headers 120 a and 120 b totransfer heat from the heat load 50.

More particularly, via cooling water return header pump 210, the heatedcooling water return from the heat load 50, representing the transfer ofheat Q₀ to the cooling water return header 120 a on the suction side ofthe cooling water return header pump 210, is in fluidic communicationwith the cooling water return header pump 210. As described in moredetail below with respect to FIG. 1, the cooling water return dischargesfrom the cooling water return header pump 210 to a heat exchange memberor heat rejection member, e.g., heat rejection coils 302 that areincluded in an evaporative recirculation cooling cycle 300 that isgenerally disposed in a middle or first evaporative section 102 b of thecooling tower 102. The first evaporative section 102 b of the coolingtower 102 is disposed adjacent to, and vertically above, the lowersection 102 a.

The cooling water flowing through the heat rejection coils 302, whichhas been cooled, as illustrated by the transfer of heat Q_(RC) from theheat rejection coils 302, is returned to cool the generalized heat load50 via the cooling water (or refrigerant or process fluid) supply header120 b. Thus, the heat load Q₀ at 50 is in thermal communication with theevaporative recirculation cooling cycle 300 via cooling water (orrefrigerant or process fluid) supply header 120 b.

The evaporative recirculation cooling cycle 300 includes one or morerecirculation fans 310 and also a water spray sub-system that includesfirst and second spray nozzle headers 3201 and 3202 that are in thermaland fluidic communication with the heat rejection coils 302.

As explained in more detail below, due to the pressure of the water inthe spray nozzle headers 3201 and 3202, a spray of water is establishedfrom the spray nozzles 320′ in the spray nozzle headers 3201 and 3202into the first fluid, e.g., air or an air and water mixture. Within thefirst evaporative section 102 b of the cooling tower 102, the firstfluid is circulated across the fluid coils 302 via the recirculationfans 310 as shown by arrows A, resulting in the transfer of heat Q_(RC)from the heat rejection coils 302 to the first fluid in the direction ofarrow A, such that the first evaporative section 102 b is configured tocirculate the first fluid to enable heat transfer Q0 from the heat load50 to the first fluid.

The percentage of entering air is regulated by the air intake dampers104′ and exhaust relief dampers 106′ based upon an enthalpy controloutside air wet bulb temperature sensor (TS) 14 disposed on the freshair intake hood 104 in the vicinity of the intake air inlet pathwayrepresented by the arrow 10. Thus, the first fluid may include air andthe air intake pathway 10 is in fluid communication with the firstevaporative section 102 b to enable the flow of air external to theevaporative cooling system 100 into the first evaporative section 102 b.The wet bulb temperature sensor 14 senses the wet bulb temperature ofthe air that is external to the evaporative cooling system 100.

The cooling tower 102 may include an upper section or second evaporationsection 102 c disposed adjacent to, and vertically above, the firstevaporation section 102 b to enable fluid communication between thefirst evaporation section 102 b and the second evaporation section 102c. Within the upper section or second evaporation section 102 c, thefirst fluid is circulated across the fluid coils 302 via therecirculation fans 310, as shown by arrows A, is discharged from therecirculation fans 310 into the upper section 102 c which may includeevaporation coils 331 and 332 (e.g., “micro0channel coils”).

The first fluid is circulated across the evaporation coils 331 and 332in the direction shown by arrows B. The first fluid, traveling in thedirection shown by arrows B, is then circulated from the upper or secondevaporation section 102 c to the spray nozzles 320′ and fluid coils 302to again travel in the opposite direction shown by arrows A. Themovement of the first fluid (e.g., air or a mixture of air and waterspray) is forced into the direction shown by arrows B above a potablewater basin or vessel 340 positioned above the evaporation coils 331 and332. It can be appreciated that the one or more fans 310 are thusconfigured to recirculate the first fluid through the first and secondevaporative sections 102 b and 102 c.

In the exemplary embodiment of FIG.1, the liquid refrigerant assistcycle 200 is implemented by providing a first liquid refrigerant assistcircuit 2001 of a first liquid refrigerant distribution unit 211 and asecond liquid refrigerant assist circuit 2002 of a second liquidrefrigerant distribution unit 212 that are functionally mirror images orduplicates of each other. That is to say, although generally thecapacity and sizing of the second evaporation coil 332 and second liquidrefrigerant distribution unit 212 are the same as the capacity andsizing of the first evaporation coil 331 and first liquid refrigerantdistribution unit 211, the capacity and sizing may differ one from theother, depending on the particular design requirements or choices. Thefirst liquid refrigerant assist circuit 2001 is dedicated to, and influid communication with, the first evaporation coil 331 while thesecond liquid refrigerant assist circuit 2002 is dedicated to, and influid communication with, the second evaporation coil 332.

Accordingly, the first and second evaporation coils 331 and 332 are influid communication with the first and second liquid refrigerant assistcircuits 2001 and 2002 via first liquid refrigerant assist cycle supplyheaders 201, 202 and first liquid refrigerant assist cycle returnheaders 251, 252, respectively.

As liquid refrigerant is supplied to first and second evaporation coils331 and 332 via the first liquid refrigerant assist cycle supply headers201, 202, the liquid refrigerant is at least partially vaporized bytransfer of heat Q1, Q2, from the first and second evaporation coils 331and 332 such that at least partially vaporized refrigerant in the formof a gas or a gas and liquid refrigerant mixture is returned via liquidrefrigerant assist circuit return headers 251, 252 to evaporators 261,262, included within first and second liquid refrigerant assist circuits2001 and 2002, respectively.

Within the evaporators 261, 262, heat Q3, Q4 is transferred from the gasor gas and liquid refrigerant mixture such that condensation of theliquid refrigerant occurs within the evaporators 261, 262 and liquidrefrigerant is discharged via evaporator to liquid receiver supply lines253 and 254 to liquid receivers 255 and 256, respectively. The liquidrefrigerant receivers 255 and 256 are operated to maintain a supply ofliquid refrigerant on the suction sides of liquid refrigerant pumps 257and 258, which discharge liquid refrigerant into the liquid refrigerantassist cycle supply headers 201 and 202 to supply liquid refrigerantagain to the evaporation coils 331 and 332, respectively.

Thus, the liquid refrigerant distribution unit is in thermalcommunication with the second evaporative section 102 c and isconfigured to circulate a second fluid, i.e., the first liquidrefrigerant flowing in the first liquid refrigerant assist cycle supplyheaders 201, 202 and first liquid refrigerant assist circuit returnheaders 251, 252, respectively, thereby enabling heat transfer Q1 and Q2from the first fluid that includes an air or a mixture of air and waterspray to the second fluid, i.e., the first liquid refrigerant.

Flow of the gas or gas and liquid refrigerant mixture may be bypassedaround the secondary evaporator coils 331 and 332 utilizing secondaryevaporator coil bypass valves 259 and 260, respectively. The bypassvalves 259 and 260 provide direct fluid communication between the liquidreceivers 255 and 256 and the liquid refrigerant assist cycle supplyheaders 201 and 202, respectively, and thus assures a minimum level ofliquid refrigerant in the respective receivers 255 and 256 under allload conditions.

Thus, a portion of the liquid refrigerant in the liquid refrigerantassist cycle supply headers 201 and 202 is bypassed around theevaporator coils 331 and 332, respectively. Bypassing of a portion ofthe liquid refrigerant in the liquid refrigerant assist cycle supplyheaders 201 and 202 in this manner with modulation of the bypass valves259 and 260 to increase the percent-open position, increases liquidrefrigerant flow to the respective receivers 255 and 256 as the heatload Q0 at 50 diminishes. This provides more precise control over thecooling process.

The circulation or flow of a second fluid, e.g., a first liquidrefrigerant, from the evaporators 261 and 262 to the evaporator coils331 and 332 via the liquid refrigerant pumps 257 and 258 and the liquidreceivers 255 and 256, and back to the evaporators 261 and 262 as a gasor a gas and liquid refrigerant mixture, define first liquid refrigerantcircuits.

The heat flow Q3 and Q4 is transferred within the evaporators 261 and262 from the condensation side represented by the flow of gas or gas andliquid refrigerant mixture in the liquid refrigerant assist circuitreturn headers 251, 252 to the liquid refrigerant assist cycle supplyheaders 201, 202 to the trim evaporation side of the evaporators 261 and262. The trim evaporation side is represented by the flow to theevaporators 261 and 262 of a second liquid refrigerant flowing in secondliquid refrigerant circuits or trim compressor circuits 2003 and 2004 ofthe first and second liquid refrigerant distribution units,respectively.

The trim evaporation side is also represented by the second liquidrefrigerant trim circuits 2003 and 2004, in which a second liquidrefrigerant is circulated from the evaporators 261 and 262 to thecondensers 269 and 270 such that the second refrigerant is received inliquid form from the condensers 269 and 270 via the second refrigerantcondenser to the evaporator supply lines 273 and 274. The secondrefrigerant in liquid form is then evaporated in the evaporators 261 and262 via the transfer of heat Q3 and Q4.

The at least partially evaporated second refrigerant, evaporated via atrimming method, flows or circulates from the evaporators 261 and 262 tothe suction side of trim compressor 265 and 266 via evaporator tocompressor suction connection lines 263 and 264, respectively. The trimcompressors 265 and 266 compress the at least partially evaporatedsecond refrigerant to a high pressure gas having a pressure range ofapproximately 135-140 psia (pounds per square inch absolute) if spraynozzle headers 3201 and/or 3202 are not operating. If spray nozzleheaders 3201 and/or 3202 are operating, the pressure range isapproximately 100-115 psia. The high pressure second refrigerant gascirculates from the discharge side of compressors 265 and 266 to thecondenser side of condensers 269 and 270 via compressor discharge tocondenser connection lines 267 and 268. Heat Q5 and Q6 is transferredfrom the condenser side of condensers 269 and 270 to the water sides ofthe condensers 269 and 270.

The system return water (or refrigerant return fluid) 120 a to the heatrejection coil 302 transports the heat Q₀ from the system heat load 50.The temperature of the return water 120 a varies based on the internalload 50 that is present. The system supply water 120 b is cooled to adesired setpoint as monitored by a temperature sensor or switch (TS) 122disposed in the supply water discharge 120 b generally close to the heatload 50.

In order to increase the efficiency of cooling the load side Q0 of thesystem 50, the fluid temperature at temperature sensor or switch (TS)122 in system supply water header 120 b is maintained as low as requiredby utilizing a mixed air enthalpy sensor (ES) 312 disposed in atmospherechamber 304 on the air intake side of the heat rejection coil 302 in thevicinity of the spray nozzle headers 3201 and 3202. The mixed airenthalpy sensor 312 senses the enthalpy of the air flowing across theheat rejection coil 302 and controls the intake air temperature to theheat rejection coil 302. There are various methods of cooling the intakeair flowing in the evaporative recirculation section 102 b to the heatrejection coil 302, including modulating the air intake and reliefdampers, 104′ and 106′, and/or pumping water through the spray nozzleheaders 3201 and/or 3202.

Cooling the intake air to the heat rejection coil 302 also occurs byoperating the primary evaporator cooling coil 331. Operation of theprimary evaporator cooling coil 331 is initiated by energizing theliquid refrigerant pump 257 thereby causing liquid refrigerant to flowto the primary evaporator cooling coil 331 from the liquid receiver 255in the first liquid refrigerant assist circuit 2001. The level ofcooling of the mixture of air and water spray, traveling in thedirection shown by arrows B, at the primary coil 331 can be furtherenhanced by energizing the trim evaporator circuit 2003 and itsassociated compressor 265. The trim compressor evaporation circuit 2003is generally in operation to cool the first liquid refrigerant assistcircuit 2001.

The secondary cooling evaporator coil 332 can further cool the air orair and water spray stream traveling in the direction of the arrows B byinitiating the liquid refrigerant trim pump 258. The temperature of theair or air and water spray stream B can be further reduced by initiatingthe secondary trim compressor evaporation circuit 2004. The secondarytrim compressor 266 is energized and cycled to maintain a set pointtemperature using the enthalpy sensor ES 312 in the air chamber 304.

In addition to controlling the temperature in the system water supplyheader 120 b to a desired value, evaporative recirculation cooling cycle300 can be utilized to extract clean water from the air stream travelingin the direction of arrow A. The evaporator coils 331 and 332, andrespective associated trim circuits 2003 and 2004, can be energized toreduce the temperature of the air flow at the location of arrows Bsufficiently below the dew point, in order to extract pure water fromthe air stream.

Pure water may be extracted from the air stream by drawing high latentair from the environment into the evaporative cooling system 100 throughthe air intake dampers 104′ indicated by arrow 10 at the air intake hood104, and/or by processing the spray water in the spray water headers3201, 3202, which is essentially grey or untreated water 352. The greyor untreated water 352 is supplied to the water side of the condensers269 and 269 from a grey water storage vessel, e.g., hot water basin 350,located or disposed in the middle section 102 b of the cooling tower 102below the heat rejection coils 302 but above the lower section 102 a ofthe cooling tower 102 that functions as the Cooling Distribution Unit(CDU) mechanical section.

The grey or untreated water 352, which is at a temperature ranging fromapproximately 60° F. (degrees Fahrenheit) to approximately 76° F., issupplied to the water side of the condensers 269 and 270 via a hot waterbasin to condenser connection lines 3203 and 3204, respectively. Grey oruntreated water 352 from outside of the evaporative cooling system 100can also be supplied to the hot water basin 350 via a grey or untreatedwater supply line 354.

Thus, the spray water sub-system is coupled to the grey water storagevessel 350. The grey water storage vessel 350 forms the water supply forthe water spray sub-system.

By lowering the temperature at primary evaporator coil 331 by increasingthe heat transfer Q1, and further lowering the temperature of the airflowing in the direction of arrow B at secondary evaporator coil 332below the dew point, pure water can condense on, and drip down from,evaporator coil 331 and/or evaporator coil 332, and collect in potablewater basin or vessel 340 as potable water 342. The potable water 342 isdischarged from the potable water basin or vessel 340 via an effluentline 344 and can be further treated by optional ultraviolet (UV) light346 located in the effluent line 344. The potable water 342 can bedirected to a potable water storage tank or reservoir 348, via effluentline 344′ downstream of the UV light 346, for other uses, or the potablewater 342 in the effluent line 344′ downstream of the UV light 346 thathas been treated via the UV light 346 can be returned to the potablewater basin 340 via a connecting line (not shown) between the downstreameffluent line 344′ and the potable water basin 340.

On the water side of the condensers 269 and 270, the temperature of thegrey or untreated water 352 varies based on the atmospheric condition atfresh air intake hood 104 in the vicinity of the intake air inletrepresented by the arrow 10, and within the atmosphere chamber 304. Thetemperature of the water 352 in the hot water basin 350 may vary fromapproximately 60° F. to approximately 80° F. degrees based on anapproximately 4° F. degree approach temperature to the available wetbulb temperature of the air in the vicinity of the intake air inlet ofthe fresh air intake hood 104 represented by arrow 10.

The temperature of the grey or untreated water 352 sprayed at the spraywater nozzle headers 3201 and 3202 may range from approximately 64° F.to approximately 76° F. The grey water 352 in hot water basin 350provides suction head to spray water pumps 3205 and 3206, which pumpspray water, i.e., grey water 352, to and through the water side of thecondensers 269 and 270 via hot water basin to condenser connection lines3203 and 3204, respectively. The grey water 352 absorbs the heat Q5 andQ6 that is rejected from the trim circuit compressors 2003 and 2004 viaheat transfer within the condensers 269 and 270, respectively.

The hot grey water 352, which may be approximately 6 to 7 degrees F.hotter at the outlet sides of condensers 269 and 270 as compared to theinlet sides, is then transported to the spray nozzles 320 in the spraynozzle headers 3201 and 3202 and sprayed via the discharge head providedby the spray water pumps 3205 and/or 3206. Water at a temperature ofapproximately 60° F. to approximately 76° F. is returned to thecondensers 269 and 270. The heat load Q0 at 50 should be equal to thedifference between the enthalpy of the exhaust air having temperature T2at relief hood 106 compared to the enthalpy of the air havingtemperature T1 at fresh air intake in air intake hood 104.

Under certain environmental conditions, such as when the environment isin the general range of, or close to, a maximum annual recordedtemperature, it may prove more efficient to operate the first liquidrefrigerant assist circuit 2001 to reduce the air temperature in theatmosphere chamber 304 without operating the compressor 265 in theprimary trim circuit 2003. The air temperature is lowered as much aspotentially possible for the particular temperature conditions of thewater intake to condenser 269 via the condenser connection line 3203from the hot water basin 350.

The balance of the heat load Q0 not being removed by the first liquidrefrigerant assist circuit 2001 and the trim circuit 2003 for the firstliquid refrigerant assist circuit 2001 can be more efficiently removedvia the secondary liquid refrigerant assist circuit 2002 and thesecondary trim circuit 2004. Thus, the compressor 266 in the secondarytrim circuit 2004 can be operated to cool or remove the remainder of theheat load Q0.

The total operating efficiency is significantly increased by thesplitting of, or staging of, the heat load Q0 into two differentportions, namely an upper portion of the heat load Q0, which is removedby operation of the first liquid refrigerant assist circuit 2001 and thetrim circuit 2003 (without operation of the trim compressor 265) and alower portion of the heat load Q0, which is removed by operation of thesecond liquid refrigerant assist circuit 2002 and the trim circuit 2004,including operation of the trim compressor 266 to lower the airtemperature below the dew point.

In one embodiment, the liquid refrigerant-assisted evaporative coolingsystem 100 includes a direct bypass connection (not shown) from the greywater 352 in the hot water basin 350 to the first liquid refrigerantassist circuit 2001 to simulate the foregoing operation of the firstliquid refrigerant assist circuit 2001 and the trim circuit 2003 withoutoperating the trim compressor 265 to remove the upper portion of theheat load Q0.

Although not explicitly illustrated in the figures, those skilled in theart will recognize that a controller may be configured and applied tocontrol the operation of the one or more fans 310 and the first andsecond liquid distribution units 211 and 212 based on the wet bulbtemperature sensed by the wet bulb temperature sensor 14 and theenthalpy sensed by the enthalpy sensor 212.

In one embodiment, a discharge cool air hood 108 is positioned in theupper section 102 c of the cooling tower 102 in the vicinity of thedownwind side of the air or air and water mixture exiting from secondaryevaporator coil 332, which travels in the direction of the arrows B. Aset of discharge cool air hood dampers 108′ are positioned to allow atleast a portion of the air or air and water mixture flowing in the Bdirection to discharge tangentially through the discharge cool air hooddampers 108′ as cool air into the surrounding environment as indicatedby the arrow 30. The flow of the cool discharge air 30 can be controlledby the set of dampers 108′. This cool or cold air is a by product of theevaporation process occurring at evaporator coils 331 and 332. Thetemperature T3 of the air or air and water mixture discharging from thedischarge cool air hood dampers 108′ at arrow 30 is generally low,approximately 55° F. to approximately 60° F., when the evaporativerecirculation cooling cycle 300 is energized for water reclamationand/or enthalpy control by utilizing the mixed air enthalpy sensor (ES)312 disposed in atmosphere chamber 304 on the air intake side of theheat rejection coil 302 as described above.

The relief hood 106 and exhaust or relief dampers 106′ are positionedwithin the upper section 102 c of the cooling tower 102 on a side of thecooling tower that is opposite to the side of the cooling tower on whichthe intake hood 104 and intake dampers 104′ are positioned in the secondsection 102 b.

A portion of the air and water spray mixture circulating in thedirection of the arrows B in the upper section 102 c may be divertedthrough the relief dampers 106′ to flow in a direction opposite to thedirection indicated by arrows B, as shown by arrow D.

Thus a circulatory flow of air and water spray mixture is created withinthe middle and upper sections 102 b and 102 c, respectively. Heat Q7that is removed from the relief hood 106 is a function of the differencebetween temperature T2 of the air or air and water mixture flowing inthe direction of the arrow 20, the temperature T3 at the discharge ofthe cold air dampers 108′ at the cold air discharge 108, the temperatureT1 at the fresh air intake 10 as monitored by temperature sensor 14, andthe heat load Q0 at 50. The heat Q7 is a function of the enthalpycontrol achieved by utilizing the mixed air enthalpy sensor (ES) 312disposed in atmosphere chamber 304 on the air intake side of the heatrejection coil 302 as described above.

As can be appreciated from the foregoing description, the air at theintake 10 and at the exhaust air discharge 30 can be varied from 100%fresh air to 0% fresh air depending on the load and the environmentalconditions, and the desired operational modes such as: water recovery(condensation), free cooling liquid refrigerant assist or a combinationof modes. During water recovery, condensation occurs at the potablewater storage vessel 340 while a portion of the heat load Q0 at 50 isrejected to the environment.

FIG. 2 illustrates one embodiment of the present disclosure in which theheat rejection coil 302 and the first and second spray nozzle headers3201 and 3202 are tilted above the grey water 352 in the hot water basin350 at an angle Θ with respect to the horizontal. The heat rejectioncoil 302 is pivotally supported by a support member 322 attached to theunderside of the potable water basin 340. The first and second spraynozzle headers 3201 and 3202 are rotatable around pivotal joint members3201′ and 3202′ located upstream from the spray nozzles 320′ in each ofthe spray nozzle headers 3201 and 3202, respectively.

This tilted configuration of the heat rejection coil 320 and the spraynozzle headers 3201 and 3202 above the grey water 352 allows forincreased evaporation of the grey water 352 due to the more directimpact of the air flow A on the surface of the grey water 352. The angleΘ can vary from about 90 degrees as illustrated by the position of theheat rejection coil 302 and the spray headers 3201 and 3201 in FIG. 1 toabout 0 degrees, in which case the heat rejection coil 302 and the sprayheaders 3201 and 3201 are essentially horizontal and parallel to thesurface of the grey water 352.

Comparing the evaporative cooling system 100 to conventional evaporativecooling tower, in view of the foregoing disclosure, the power input tothe spray water pumps 3205 and 3206 is generally the same as for aconventional evaporative cooling tower, e.g., about 5 Horsepower (HP) toabout 7.5 HP (about 3.75 KW (kilowatts) to about 5.65 KW). The powerinput to the compressors 265 and 266 is generally scalable over a rangeof about 40 tons to about 90 tons (about 141.3 KW to about 317.7 KW) ofrefrigeration with generally a maximum power consumption of about 0.25KW/ton of refrigeration. The power input to the fans 310 is generallyabout the same power input to the fans of a conventional evaporativecooling tower, e.g., about 25 HP to about 40 HP (about 18.75 KW to about30 KW) and the power is proportionally regulated via variable frequencydrive of the fan motors (not shown).

The reclamation of water is advantageous as compared to conventionalmethods which provide no water reclamation. During the water reclamationprocess, the compressors 265 and 266 operate in a very efficient mode interms of kilowatts (KW)/ton of refrigeration and the operation can bevaried as necessary to match the Q1 and Q2 heat removal requirements.The resulting operation may achieve a reduction in water consumption ofabout 93% to about 97% as compared to the water consumption of aconventional evaporative cooling tower. The remaining about 3% to about7% of the water, respectively, is generally blown down from the coolingtower 102 to remove solids in the potable water basin 340 and the hotwater basin 350. Although in principle all of this water can berecovered, the energy consumption would increase significantly.

What is claimed is:
 1. An evaporative cooling system for cooling a heatload, comprising: a first evaporative section configured to circulate afirst fluid to enable heat transfer from the heat load to the firstfluid; a second evaporative section in fluid communication with thefirst evaporative section, the second evaporative section configured tocirculate the first fluid; and a liquid refrigerant distribution unit inthermal communication with the second evaporative section, the liquidrefrigerant distribution unit configured to circulate a second fluid toenable heat transfer from the first fluid to the second fluid.
 2. Theevaporative cooling system of claim 1, wherein the first fluid is amixture of air and water, and the second fluid is refrigerant.
 3. Theevaporative cooling system of claim 2, wherein the first evaporativesection comprises a heat exchange member, wherein the heat of the heatload is transferred to the first fluid as an air and water mixtureflowing across the heat exchange member.
 4. The evaporative coolingsystem of claim 3, wherein the first evaporative section furthercomprises a water spray system configured to spray water into to therecirculating flow of the air and water mixture flowing across the heatexchange member.
 5. The evaporative cooling system of claim 4, whereinthe water spray system is coupled to a grey water storage vesseldisposed below the heat exchange member, wherein the grey water storagevessel forms a water supply for the water spray system.
 6. Theevaporative cooling system of claim 1, wherein the liquid refrigerantdistribution unit comprises a first liquid refrigerant distribution unitand a second liquid refrigerant distribution unit, and wherein thesecond evaporative section comprises a first evaporation coil in fluidcommunication with a first liquid refrigerant assist circuit of thefirst liquid refrigerant distribution unit.
 7. The evaporative coolingsystem of claim 6, wherein the second evaporative section furthercomprises a second evaporation coil in fluid communication with a secondliquid refrigerant assist circuit of the second liquid refrigerantdistribution unit.
 8. The evaporative cooling system of claim 1, whereinthe liquid refrigerant distribution unit comprises a liquid refrigerantassist circuit in fluid communication with the second evaporativesection.
 9. The evaporative cooling system of claim 8, wherein the firstfluid is a first refrigerant, and wherein the liquid refrigerantdistribution unit further comprises a trim compressor circuit, in whicha second refrigerant flows, in thermal communication with therefrigerant flowing in the liquid refrigerant assist circuit.
 10. Theevaporative cooling system of claim 9, wherein the liquid refrigerantdistribution unit comprises a second liquid refrigerant assist circuitin fluid communication with the second evaporative section.
 11. Theevaporative cooling system of claim 10, wherein the liquid refrigerantdistribution unit further comprises a second trim compressor circuit, inwhich the second refrigerant flows, in thermal communication with thefirst refrigerant flowing in the second liquid refrigerant assistcircuit.
 12. The evaporative cooling system of claim 1, wherein thesecond evaporative section further comprises at least one evaporationcoil in fluid communication with the liquid refrigerant distributionunit.
 13. The evaporative cooling system of claim 12, wherein the atleast a portion of the first fluid recirculating in the firstevaporative section is condensed into a potable water receiving vesseldisposed below the at least one evaporation coil.
 14. The evaporativecooling system of claim 13, further comprising a conduit in fluidcommunication with the potable water receiving vessel to enable flow ofpotable water from the evaporative cooling system.
 15. The evaporativecooling system of claim 1, wherein the first fluid is air, theevaporative cooling system further comprising: an air intake pathway influid communication with the first evaporative section to enable theflow of air external to the evaporative cooling system into the firstevaporative section; and a wet bulb temperature sensor disposed in theair intake pathway for sensing the wet bulb temperature of the airexternal to the evaporative cooling system.
 16. The evaporative coolingsystem of claim 15, further comprising: a heat rejection member disposedin the first evaporative section to enable the cooling of the heat load;an enthalpy sensor disposed in proximity to the heat rejection memberconfigured to sense the enthalpy of the air flowing across the heatrejection member; at least one fan configured to recirculate the airthrough the first and second evaporative sections; and a controllerconfigured to control the at least one fan and the liquid refrigerantdistribution unit based on the wet bulb temperature sensed by the wetbulb temperature sensor and the enthalpy sensed by the enthalpy sensor.